On 8/23/2018 7:27 PM, Mike S wrote:
On 8/23/2018 5:20 PM, wrote:
On Thu, 23 Aug 2018 16:48:41 -0700, Mike S wrote:

I bought a SanDisk Ultra 64GB microSDXC card for my Moto X4 phone so I
could have music on it. I have a SIIG USB 2.0 Multi Card Reader/Writer
that is several years old. The specs include: "Compliant with Universal
Serial Bus 2.0 Specification, Support up to 64GB memory card capacity,
Reads a variety of CF, xD, SD, SDHC, miniSD, microSD..."
One issue I found is when I first started saving files to the card
Windows 7 File Explorer reported that it was writing at 9.1MB/s, but I
notice that the speed steadily drops.
The next issue is that the card didn'preserve files beyond 7.16 GB,
twice it corrupted the files and Windows prompted me to Scan and Fix the
card when it was plugged into the card writer.
Also the write speed can vary now from about 3MB/s to 1 MB/s.
Does this sound like a bad card? It was only $15. Or could this be a bad
SIIG USB card writer?
I'm going to look around for a friend with a computer that has a built
in SD slot to see if I can rule out the SIIG.


Â* My oldÂ* T500Â* Vista era Â* laptopÂ* is much faster when using the
built-in SD card readerÂ* -Â* when compared withÂ* usb cable -
- to theÂ* dash camÂ* orÂ* digital camera ..
- sorry -Â* I'm not a techieÂ* to explain why .. or know if this helps.
Â*Â* John T.

Thanks John,
I got access to an HP w7 and am formatting the SD card now, I'll try
writing the files with that, am guardedly optimistic after reading your
post. Thanks.
Mike

I copied files from my desktop to a USB powered external hdd (22.5 MB/s)
then copied from that to the SD card using an HP w7 laptop, the speed
decreased steadily until it leveled off around 4 MB/s copying 26.4 GB
4,138 files, these were the copy speeds:

9.10 MB/s at start
5.04 MB/s at 50%
4.21 MB/s at 75%
3.93 MB/s at 99%

When the copy operation was completed using dir /s *.mp3 the hard drive
showed total files listed as 3532 files (28,369,825,845 bytes) while the
SD card showed total files listed 1307 files (10,990,908,726 bytes) so I
think I have a bad SD card.

Is this kind of drop in write speeds for long write operations normal?
If so, is it a function of heat, so doing multiple smaller writes then
cooling the SD card might result in significant time savings?